Telephone-exchange system.



H. P. CLAUSEN.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED APR-24.1917. l9llfi66= Patented Jan. 21,1919. 2SHEETS-SHEET //1 v/vfox- Hem y f. C/ause/v.

H. P. CLAUSEN. TELKPHONE EXCHANGE SYSTEM. APPLICATION mas APR.2-1, 2912.

u ll.

Pzaented Jan, 21,1919.

2 SHEETS-SHEET 2.

a F M.

UNITED STATES PATENT orrroa.

Heme? P. onausniv, 'oi 'ivroni'vrvnnnoiv, NEW YoRxgassieiv'oR 'ro'WESTERN ELECTRIC COMPANYQINCoRP'oRA'rED,or NEW YORK, N. Y., ACORPORATION or NEW YORK.

"'rniiiii iroivii nxcnlinen SYSTEM.

fifiecification of Letters Patent.

Patented Jan. 21, 1919.

hppncationnieu-Aprii 24, 1917. SerialNo. 164,232.

To all whom it may concern:

Be it knownth'atI, HEN Y P. Cngiuslm, a citizen of the United States',"res1d1ng--at "Mount Vernon, in the county ofjllfestchester and State ofNew York, hav'e' nvented'certain' new and useful" Improvements inTelephone-Exchange Systems, of which the fol- 'lowin 1s a *full "clearconcise-and exact description.

This invention relates to 1 telephonefexchange systems, and' moreparticularly to such systems of the central'energy type, ts

' object being the provisionof improved" signahng means for systemsof'tlns character. I

In accordance with a=featureofthisinvention, atelephonesystemcomprisi-ng telephone lines andlink" circuits is providedwith asignal'commonto the link circuits which may be connected with anengaged link circuit and operated upon the opening and subsequentclosing of the 'linecircuit connected with the engaged link circuit tofurnish a recall-signal.

This invention is illustrated in the accompanying drawings, wherelnFigure '1 shows a link circuit containing one embodiment of thisinvention; and Fig. 2 shows a link circuit containing another embodimentof this inventlon.

For convenience likeparts in the two figures will be designated by thesame reference characters.

Fig. 1.

In Fig. 1 there are shown two ordinary telephone lines A and B, whichextend from telephone stations to a central ofiice, at which is locateda plurality of link circuits, one of which is shown at C. Located at thecentral oflice,'and common to the link circuits,*is' an automatic finderswitch'comprising a stepby-step actuated ratchet wheel 6 carrying thecontact brush 7 which, when the ratchet wheel is being rotated, isadapted to successively engage terminals which are severally connectedto the different link circuitsto which the finder switch is common. Astepping niagnet 8 controls an armature 9 and pawl 10, which,when thestepping magnet is operated, causes the ratchet Wheel to make one-stepadvancements, moving its brush 7 from terminal to terminal. A startrelay 11 is adapted, when energized, to close the stepping cirruit ofstepping magnet 8, and a stop magnet 1.2 is-adapted, when enerthefollowing manner.

gized, to open the steppingcircuit. A'signaling'devi'ce' 13 iscontrolled bythe stop magnet 12 and operates as a flashing signal:uponthe operation of the stop magnet 12.

Referring now to the operation of the system shown in Fig. 1', it willbe assumed that subscriber A initiates a call in the-usual manner. Theoperator then inserts answering plug 20 into line jack21, whereuponlocal circuit relay 22, cut-off relay 23' and supervisory relay 24operate. The operator may now actuate listening key25 toconnect anoperators telephone set to the talking strands of cord circuit C. Uponbeing advised that the subscriber A desires tobe connected with the lineof subscriber B, the

operator restores the listening key 25 to normal position "and insertscalling plug 26 intoline jack 27 of line B, whereupon local circuitrelay 28 and cut-off relay'29 operate. The operation of the localcircuit relay 28 causes calling supervisory lamp 30 to be lighted. Theoperator may now actuate ringing key 35 to connect ringing current tothe line of subscriber B for operating the call bell at that station. Inresponse to the observing the disconnect signals removes the .plugs fromthe jacks, whereupon the apparatus is returned to normal position.

Suppose, however, that before the plugs are withdrawn from the jackssubscriber A wishes to initiate another connection. In

'so doing, the receiver is removed from the switchhook, whereupon theanswering supervisory lamp 37 is lighted continuously and the commonlamp 13 is lighted intermittently to furnish a characteristic signal tothe operator. This is accomplished in When subscriber A originallyrestored the receiver to the switchhook, the release of thesupervisoryrelay 24. caused the operation of startrelay .11 and relay 38 over acircuit from battery through the winding oi start relay 11-, co1n+pletes a locking circuit for itself through its left-hand alternatecontact, which removes this relay from under control of the answeringsupervisory relay 24. The operation of the start relay 11 completes anoperating circuit for the lamp 13, whereupon this lamp operatescontinuously, and

also completes the stepping circuit of stepping magnet 8. This steppingcircuit includes an interrupter'41 so that in the rotation of theinterrupter 41, the stepping magnet 8 is intermittently energized,causing the one step advancement of the brush 7 from terminal toterminal. After the automatic finder switch has been started inoperation, the removal of the receiver from the switchhook by thesubscriber A causes the operation of answering supervisory relay 24,whereupon, when the brush 7 of the automatic finder'switch comes intoengagement with terminal 2 connected to the cord circuit C, stop magnet12 is operated and answering supervisory lamp 37 is lighted over acircuit from battery through the lamp .37, alternate contact of thesupervisory re- 7 lay 24, right-hand alternate contact of relay 38,terminal 2 and brush? of the automatic finder switch, contact 42 of akey 43 (which is common to the link circuits) and the winding of stopmagnet 12 to ground. The operation of the stop magnet 12 opens thestepping circuit of the stepping magnet 8. The brush 7 remains inengagement with terminal 2. The energization of the stop magnet 12 alsoincludes an interrupter 44 in circuit with the lamp 13, whereupon thislamp is intermittently lighted.

It will be observed that the answering supervisory lamp 37 is lightedcontinuously when relay 24'is deenergized to serve as a disconnectsignal and is also lighted continuously when the connected callingsubscriber has initiated asecond call before the cord circuit C has beendisconnected from the line. The operator observing the flashing of thecommon lamp 13 knows that one of the calling subscribers connected withthe various cord circuits, which may be plugged up into the lines, hasmade a recall. If only one answering supervisory lamp'is glowing theoperator will know that thecalling subscriber connected with the cordc1rcu1t, wlth which that answering supervisory lamp 1s assoclated, hasmade the recall and may, therefore, actuate the listening key to connectthe telephone set to the cord circuit. In actuating the listening key,contact 40 in the locking circuit of locking relay 38 and start relay 11is thereupon opened, releasing these-relays. Relay 38,

in releasing, opens the circuit of the answering supervisory lamp 37 andthe stop magnet 12. The lamp 13 is then extinguished. Start relay 11, inreleasing, opens the step ping circuit of stepping magnet 8, whereuponthe finder switch is free to be connected with another cord circuit onwhich a recall is being made. Upon being advised of the connectiondesired, the operator may withdraw the calling plug from the jack ofline B and after restoring a listening key to normal, may insert thecalling plug into the jackof any line desired. The connection will thenbe completed in the manner heretofore described. It will be observedthat when the listening key is restored to normal, the contact 40closes.- This. does not cause the operation of the locking relay 38 andthe start relay 11 or the stepping and stop magnets 8 and 12 for theanswering supervisory relay 24 is nowenergized.

Suppose, however, that when the opera tor observed the flashing of thecommon lamp 13 she had also observed more than one answeringvsupervisory lamp glowing. It would not then be possible to determinewhich of the several calling subscribers had made the recall. Theoperator would, therefore, actuate key 43, which would close contact 45,thereby establishing a maintaining circuit for the stop magnet 12 andwould open contact 42 in the operating circuit of the answeringsupervisory lamp 37. This lamp would then be effaced and would therebyserve as an indication to the operator that calling subscriber A,connected with the cord circuit shown, had made the recall. Afterdetermining the cord circuit on which the recall had been made, theoperator would restore key 45 to normal position and actuate thelistening keyof the proper cord circuit to connect thereto the operatorstelephone set.

The operations following the actuation of the listening key of this cordcircuit would take place in the order hereinbefore mentioned.

Fig. 2.

The system shown in Fig. 2 is provided with apparatus by means of whichthere may be coiiperation between operators at adjacent positions,whereby greater efficiency in the handling of both original calls andrecalls is obtained. This result is accomplished by providing at theoperators position at which cord circuit C is located, designated asoperator No. 2, and at the operators positions to the left and rightthereof, designated respectively as operators No. 1 and No. 3,non-locking keys 50, 60 and common to the respective operatorspositions. By the actuation of the common listening key at the position,any one of the'three operators may determine the cord circuit on which arecall hasb'een made; In this F ig; 2, the automatic finder switchdiiiers slightly from that shown in Fig. l,in that its rotatable arm 7is equipped with three brushes 81, 82 and 83 adapted-to successivelyengage sets of three terminals to which are connected circuit leads ofthe different cord circuits of the position, there being one set ofterminals for each cord circuit. The brush 81-is for the same purpose asthe simple contact arm 7 of Fig. 1, while the two brushes 82and 83' areconnected by leads to normally open contacts of common listening keys51, 61 and 71 at the operators positions No. 1, No. 2 and No; 3,respectively. The normally open contacts are connected in multiple, sothat any one of the three operators, when the finder switch is connectedwith a cord circuit on which there is'a recall, may, by the actuation ofthe common listeningkey of the position, connect thehasso'ciated,telephone set with the particular cord circuit.

Referring now tothe operation of the system disclosed in Fig. 2, it willbe assumed that subscribers A and Bare connected together by means ofthe cord circuit C and that the receivers are removed from theswitchhooks and the subscribers-are in conversation. ,Cut ofi relays 23and 29, as well as theloc'al circuit relays 22mid 28 and the supervisoryrelays 24 and 36 are therefore operated; At the{con'c1usion of theconversation the subscribers restore the receivers to the switchhooks,releasing the supervisory' relays 24 and'36, whereupon the supervisorylamps 37 and 30 are lighted to fur nish disconnect signals.

Suppose, now, that before the plugs are withdrawn from the jacks thecalling subscriber initiates another call. In so doing the answeringsupervisory lamp 37will be lighted continuouslyand the common lamp '13will be lighted intermittently to furnish to the operator acharacteristic signal. The manner in which this is accomplished is asfollows; Upon the'restoration of the receiver to theflswitchhook bysubscriber A, answering supervisory relay 2% releases, as beforedescribed. The release of this relay causes the operation of start relay11 and lock-up relay 38 over a circuit from battery through theleft-hand normal contact of stop magnet 12, the winding of start relay11, contact 40 of listening key 25, winding-of relay 38 and normalcontact thereof, normal contact of answering supervisory relay 24:, andthe contact local circuit relay to ground. Lock-up relay 38, inoperating, completes a locking circuit for itself which removes 'thisrelay from under control of the answering supervisory relay 24. Thislocking circuit may be traced from battery through contact 7-1 of commonlistening key 70, contact 64 of common listening key 60, contact 54: ofcommon listening key 50, winding of start relay 11, contact 410 oflistening key 25, winding and left-hand alternate contact of lock-uprelay 38, and contact of relay 22 to ground. The operation of startrelay l1 completes a circuit for the lamp 13 to cause the continuousoperation thereof and also closes the stepping circuit of the steppingmagnet 8. This stepping circuit may be traced from battery, contact 52of common listening key 51, contact 62 of common listening key 61,contact 72 of common listening key 71, normal right-hand contact of stopmagnet 12, right-hand contact of start relay 11, the winding of steppingmagnet 8, and interrupter -11 to ground. The rotation of the interrupter-11 causes the stepping magnet 8 to be intermittently energized torotate the ratchet wheel 6 and consequently move the brushes 81,82 and83 over the sets of terminals. In themeantime the subscriber A hasremoved the receiverfrom the switchh'ook, again causing the operation ofthe answeriii'g'supcrvisory relay 24. After the operation of answeringsupervisory relay 24-, brush 81 of the automatic findei' switch comesinto engagement with terminal 90, connected with the cord circuit C, andas a resultstop magnet 12 is' -immedia-tely energized and the answeringsupervisory lamp 37 lighted over a circuit from battery through the lamp37, alternate contact of answering supervisory relay 24:, right-handalternate contact of the lock-up relay 38, terminal 90, brush 81,winding of stop magnet 12, contact 53 of key 50, contact 63 of key (50,and contact 73 of key to ground. The energization of stop magnet 12opens the stepping circuit of the stepping magnet 8, and connectsinterrupter 44L in circuit with the common lamp 13, whereupon the lamp13 is intermittently lighted while the answering supervisory lamp 37 iscontinuously lighted. Upon the opening of the stepping circuit, thestepping net 8 remains deenergized and the brushes remain. in engagementwith the set of contacts associated with the cord circuit C. Thecontinuous glowing of the answering supervisory lamp 37 and intermittentglowing of the common lamp 13 serve as a characteristic signal to thethree operators, indicating that one of the subscribers connected withthe various cord circuits in the position at which cord circuit C andthe automatic finder switch are located has made a recall. If, at thistime the cord circuit C, only, is inuse and operator No. 2 is attheposition and not busy, this operator will know that the recall hasbeen made by subscriber A and will actuate the listening key 25, therebyconnecting this operators telephone set to the cord circuit Cir C andcausing the release of the lock-up relay 38 and start relay 11, and theefiacement of answering supervisory lamp 37 and the common lamp 13. Theconnection with the desired line may be com leted in the mannerhereinbefore describe Suppose, however, that when the common lamp 13 wasglowing intermittently several cord circuits were in use and several ofthe answering supervisory lamps were glowing continuously in which case,the operators would not know which calling subscriber had made therecall. Operator No. 2 now actuates key 60, causing the answeringsupervisory lamp 37 to be intermittently lighted thereby indicating thecord circuit on which the recall was made. While the key 60 is actuated,stop magnet 12 which is of the slow release type, remains energized overa circuit from battery through the lamp 37, alternate contact ofanswering supervisory relay 24., right-hand alternate contact of lock-uprelay 38, terminal 90, brush 81, winding of stop magnet 12, contact 53of key 50, contact of key 60 and interrupter 4A to ground. The lamp '37is intermittently lighted over this circuit. This operator may restorethe common key 60 to normal position and actuate either the individuallistening key 25 associated with cord circuit C, or the common listeningkey 61, to connect the telephone set of operator No. 2 with the cordcircuit C. Should the common listening key 61 be operated, the operatorstelephone set would be connected to the cord circuit through the upperand lower alternate contacts of the common listening key 61 and thebrushes 82 and 83 of the automatic finder switch. The actuation of thecommon listening key 61 would open the contact 64 in the looking circuitof the lock-up relay 38 and contact 62 in the stepping circuit ofstepping magnet 8. Lock-up relay 38, start relay 11 and stop magnet 12are now de'cinergized and both lamps 37 and 13 extinguished. Shouldanother calling subscriber make a recall while the common listening key61 is actuated, start relay 11 would be operated to light the commonlamp 13 but the stepping magnet 8 would not be energized, for thestepping circuit is open at contact 62 of key 61.

manner operator No. 35 by first actuating key to determine the cordcircuit on which the recall is being made, then restoring this key tonormal position and actuating the common listening key 71, could take upthe recall. 7

The common keys at each position may, of course, be located so that bymoving a common lever in one direction, one key would be actuated and bymoving the lever in the opposite direction the other key would beactuated. The keys 50, 60 and 70 are preferably of the non-locking type,while the keys 51, 61 and 71 are preferably of the locking type.

The lock-up relay 38 individual .to a cord circuit is normallydeenergized and may be considered as an individualizing device which,when rendered efiective as by en ergization, cooperates with thesupervisory relay 24 to appropriate and connect the common automaticfinder switch with the cord circuit with which the effectiveindividualizing device is associated. The automatic finder switch may beconsidered as electromagnetic signal control mechanism renderedoperative for signaling purposes when connected with a cord circuit.

What is claimed is;

' 1. A telephone exchange system comprising telephone lines, linkcircuits for interconnecting the lines, a signaling device individual toeach link circuit, a signaling device common to the link circuits, asupervisory relay for each link circuit controlled over a connectedtelephone'line, an operating circuit for each individual signalingdevice for causing the continuous operation thereof completed when theassociated link circuit is connected with one of the lines and thesupervisory relay thereof is energized, and interrupter mechanismbrought into circuit with the common signaling device upon thecompletion of the operating circuit of theindividual signaling device 2.A telephone exchange system comprising telephone lines, link circuitsfor interconnecting the lines, oneofthe link circuits being connectedwith one of the lines, a. relay for the engaged link circuit controlledover a connected line, an automatic finder switch common to the linkcircuits started 7 upon the deenergization of the relay and appropriatedby and connected with the engaged link circuit when the relay thereof issubsequently energized, a signaling device, and interrupter mechanismconnected in circuit with the signaling device upon the appropriationand connection of the automatic finder switchv with the'engaged linkcircuit.

3. In a telephone exchange system comprising telephone lines, linkcircuits for interconnecting the lines, one of the link circuits beingconnected with one of the lines,

AQA telephone exchange system comprising telephone lines, link circuitsfor interconnecting the lines, one of the link circuits being connectedwith one of the lines,

a signaling device individual to each link circuit, a relay fortheengaged link circuit controlled over the connected line, an automaticfinder switch common to the link circuits started upon thedeenergization of the relay and appropriated by and connected with theengaged link circuit when the relay thereof is subsequently energized, asignaling device common to'the link circuits, and operating circuits forthe signaling device individual to the engaged link circuit and for thecommon signalin device completed upon the connection of t 'e switch withthe engaged link circuit.

5. A telephone exchangesystein comprising telephone lines, link circuitsfora'nt'erconnecting the lines, one of the link-circu ts beingconnectedwith' one of the lines, a relay for the engaged link circuitcontrolled over a connected line, an automatic finder switch common tothe link circuits, a second relay for the engaged link circuit operating.upon the de'elnergization of the first relay to start the finderswitchin operation, the finder switch being appropriated by and connected withthe enga ed link circuit upon the subsequent energizatlon of the firstmentioned relay, and a signaling device operated upon the connection ofthe switch with the engaged link circuit.

' 6. A telephone exchange system comprising telephonelines, linkcircuits for interconnecting the lines, one of the link circuits beingconnected with one of the lines, a relay for the engaged link circuitcontrolled over the connected line, an automatic finder switch common tothe link circuits started upon'the de'e'nergization of the relay andappropriated by and connected with the engaged link circuit whentherelay thereof is subsequently energized, a signaling device operatingupon the connection of the switch withthe engaged link circuit, and anoperator controlled switch for disconnecting the switch from the engagedlink circuit.

7. A telephone exchange system comprising telephone lines, link circuitsfor interconnecting the lines, one of the link circuits being connectedwith one of the lines, a supervisory relay for the engaged link circuit,an automatic finder switch commonto the latenci e fase ee relw he-en aed link circuit operating upon the denergization of the supervisoryrelay for starting the finder switch in operation, the finder switchbeing appropriated by and connected with the engaged link circuit uponthe subsequent energization of the supervisory relay, and a smnalingdevice operating upon connection 0 the finder switch withthe engagedlink circuit.

8. A telephone exchange system comprisingtele'phone'lines, link circuitsfor interconnecting the lines, one of the link circuits being connectedwith one ofthe lines, a signaling device individual to each linkcircuit, a supervisory relay for the engaged link circuit, astep-by-step finder switch common to the linkcircuits, a second relayfor the engag'ed link circuit operating upon the deenergiz'ation of thesupervisory relay to start the switch in operation, the switch beingappropriated by and connected with the engaged link circuit upon thesubsequent energization of the supervisory relay, a signaling devicecommon to the link circuits, and operating circuits for the signalingdevice individual to theengaged link circuit and for'the commonsignaling device completed ,upont'he connection of the switch with theengaged link circuit. 1

9. A telephone exchange system comprising telephone lines, link circuitsfor interconnecting the lines, one of the link circuits being connectedwith one of the lines, a signaling device individual to each linkcircuit, a supervisory relay for the engaged link circuit, an automaticfinder switch common to the link circuits, a second relay for theengaged link circuit operating upon the deenergia'ation of thesupervisory relay to start the swltch in operation, the'switchbeingappropriated by and connected with the engaged link clrcuit uponthe subsequent energiz'ation of the supervisory relay, an operatingcircuit for the signaling device individual to the engaged link circuitcompleted upon the connection of the switch to the engaged link circuit,and an operator controlled switch common to the link circuit for openingthe operating circuit.

10. A telephone exchange system comprising telephone lines', linkcircuits for inter connecting the lines, one of the link circuits beingconnected with one of the lines, a signaling device individualto eachlink circuit, a supervisory relay for the engaged link circuit, astep-by-step finder switch common to the link circuits, stepping andstopping magnets therefor, an operating circuit for the stepping magnet,a second relay for the engaged link circuit operating upon thedeenergization of the supervisory relay for completing the operatingcircuit of the stepping-magnet, and a circuit for the stopping magnetincluding the signaling device of the eea scd link: c necomp t p thegagemcnt of the switch brush with a terminal conne;ted with the engagedlink circuit when the supervisory relay thereof is ener- 'zed. 11. Atelephone exchange system comprising telephone lines, link circuits forin terconnecting the lines, a normally inefi'ective individualizingdevice for each link circuit, an electromagnetic signal controlmechanism common to the link circuits, and means common to the linkcircuits and cooperating with the individualizing device of an engagedlink circuit when rendered eflective by the restoration to and thesubsequent rcnoval from the switchhock of the receiver of the engagedline to connect'the signal control mechanism with the engaged linkcircuit and to prevent the connection thereof with any other linkcircuit.

' 12. A telephone excha ge system comprising telephone lines, linkcircuits for interconnecting the lines, one of the link circuits beingconnected with one of the lines, a normally ineli'ective individualizingdevice for each link circuit, an automatic finder switch common to thelink circuits, means controlled bv the restoration to and the subsequentremoval from the switchhook of the receiver at the connected station torender the individualizing device of the engaged link circuit effectiveto connect there with the finder switch, and a s gnaling device actuatedupon connection of the finder switch with the engaged link circuit.

13. A telephone exchange system comprising telephone lines, linkcircuits for in terconnecting the lines, one of the link circuits beingconnected withone of the lines, a supervisory relay for each linkcircuit,

a second relay for the engaged link circuit.

operating upon the deenergization of the supervisory relay, and anelectromagnetic signal control mechanism common to the link circuitsrendered individual to and connected with the engaged link circuit uponthe operation of the second relay followed by the energization of thesupervisory relay. 1 A telephone exchange system comprising telephonelines, link circuits for interconnecting the lines, one of the linkcircuits being connected with one of the lines, a supervisory relay foreach link circuit, a second relay for the engaged link circuit operatingupon the decnergization of the supervisory relay. an automatic finderswitch common to the link circuits rendered individual to and connectedwith the engaged link circuit uponthe subsequent energization of thesupervisory relay, and a signaling device actuated upon connection ofthe finder switch with the engaged link circuit.

15. A telephone exchange system comprising teleph ne lines, linkcircuits for interconnecting lines, an electromagnetic signal controlmechanism common to the link circuits, an individualizing device foreach link circuit for rendering the common signal control mechanismindividual to any one of several engaged link circuits, and meansresponsive to the closure and subsequent opening of an engaged telephoneline and cooperating with the individualizing device of thecorresponding engaged link circuit to connect the signal controlmechanism thereto to the exclusion of other engaged link circuits. I

16. A telephone exchange system comprising telephone lines, linkcircuits for interconnecting the lines, one of the link circuits beingconnected with one of the lines, a normally ineflective individualizingdevice for each link circuit, an automatic finder switch common to thelink circuits, means responsive to the opening and subsequent closure ofthe connected linecircuit for rendering the individualizing device ofthe engaged link circuit effective to connect therewith the automaticfinder switch, and a signaling device actuated upon connection of thefinder switch with the engaged link circuit. v v

17. A telephone exchange system comprising telephone lines,link circuitsfor in terconnecting ,the lines, a signal common to the link circuits,apparatus for connecting the signal to any one of several engaged linkcircuits to the exclusion of other engaged link circuits, meansresponsive to the opening and subsequent closure of an eligagedtelephone line and cooperating with the apparatus to connect the signalwith the corresponding engaged link circuit 7 and means responsive uponsuch connection for operating the signal. V 18. A telephone exchangesystem comprising telephone lines, link circuitsfor in' terconnectingthe lines, a signaling device commoi'i to the linkcircuits, switching ap'paratus for connefting the signaling device to one of severalengagedlink circuits to the exclusion of other engaged link circuits,electromagnetic mechanism responsive to the opening and subsequentclosure of an engaged telephone line for causing the switching apparatusto connect the signaling device with the corresponding engaged linkcircuit, and an. operating circuit forthe signaling device completedupon connection thereoi with the engaged link circuit.

19. A telephone exchange system com prising telephone lines, linkcircuits for interconnecting the lines, a signaling device common to thelink circuits, switching appav ratus for connecting the signaling deviceto one of several engaged link circuits to the exclusion of otherengagedlink circuits, a supervisory relay for each engaged link circuit,a second relay therefor operating upon the dee'nergization of thesupervisory relay and cooperating with the supervisory relay whensubsequently energized to cause the swltching apparatus to connect theslgnahng device with the correspondlng engaged link ,circuit, and anoperating circuit forthe signaling device completed upon connectionthereof with thecorresponding engaged link circuit.

20. A telephone exchange system comprising telephone lines, linkcircuits for interconnecting the lines, asignaling device individual toeach link circuit, a signaling d'evice common to the link circuits,switching apparatus for connecting the common sig naling device to oneof several engaged link circuits to the exclusion of other engaged linkcircuits, a supervisory relay for each engaged link circuit, a secondrelay therefor operating upon the deenergization of the supervisoryrelayand cooperating with the supervisoryrelay (when "subsequently energizedto cause the switching apparatus to connect the common signaling devicewith the corresponding engaged link oircuit,'and

" operating circuits for. the signaling device individual to the linkcircuit and for the common signaling device-completed upon connection ofthe common signaling device with the corresponding engaged link circuit.

21. A telephone exchange system comprising telephone lines, linkcircuits for interconnecting the lines, a signal common to the linkcircuits, switching apparatus for connecting the signal to any of thelink circuits, means responsive to the opening and subsequent closure ofa connected telephone line and cooperating with the switching apparatusto connect the signal with the corresponding engaged link circuit andoperate the signal, an operators telephone set, and anoperator-controlled key common to the link circuits and upon actuationcooperating with the switching apparatus for connecting the operatorstelephone set with the engaged link circuit.

- 22. A telephone exchange system comprising telephone lines, linkcircuits for interconnecting the lines, a signal common to the linkcircuits, switching apparatus for connecting the signal to any of thelink circuits, means responsive to the opening and subsequent closure ofa connected telephone line and cotiperating with the switching apparatusto connect the signal with the corresponding engaged link circuit andoperate the signal, a plurality of operators positions, an operatorstelephone set for each position, and an operator-controlled key at eachposition for connecting the operators telephone set thereof with theengaged link circuit when the signal is connected therewith.

23. A telephone exchange system comprising telephone lines, linkcircuits for interconnecting the lines, a signal individual to each linkcircuit, a signal common to the link circuits, switching apparatus forconnecting the connnon signal to one of several engaged link circuits tothe exclusion of other engaged link circuits, and means responsive tothe opening and subsequent closureof a connected telephone line andcooperating with "the switching apparatus to conncctthe common signalwith the corresponding engaged link circuit and operate both the'con'nnon signal and the signal individual to "the corresponding engagedlink circuit.

A telephone exchange system comprising telephone lines, link circuitsfor interconnecting the lines, one of the link circuits bci'ng'connectedwith one of the lines, a signal in'dividual to each link circuit, asignalcommon to the link circuits, switching apparatus for connectingthe common signal ing'telephone lines, link circuits for interconnectingthe lines, one of the link circuits being connected with one of thelines, a signal individual to each link circuit. a signal common to thelink circuits, switching apparatus for connecting the common signal toany of the link circuits, means responsive to the opening and subsequentclosure of the connected line circuit and cooperating withthe switchingapparatus to connect the common signal with the engaged link circuit andoperate both the common signal and the signal individual to the engagedlink circuit, a plurality of operators positions. and anoperator-controlled key at each position for stopping the operation ofthe individual signal of the engaged link circuit.

26. A telephone exchange system comprising telephone lines, linkcircuits for interconnecting the lines, one of the link circuits beingconnected with one of the lines, a signal individual to each linkcircuit. a signal common to the link circuits, switching apparatus forconnecting the common signal to any of the link circuits, meansresponsive to the opening and subsequent closure of the connected linecircuit and cooperating with the switching apparatus to connect thecommon signal with the engaged link circuit and operate both the commonsignal and the signal individual to the engaged link circuit, aplurality of operators positions, an operator-controlled key at eachposition for stopping the operation of the individual signal of theengaged link circuit, an operators telephone set for each position, andan op orator-controlled key at each position for connecting theoperators telephone set thereof with the engaged link circuit.

27. A telephone exchange system compris ing telephone lines, linkcircuits for interconnecting the lines, one of the link circuits beingconnected with one of the lines a signaling device individual toeachlink circuit, an automatic finder switch common to the link circuitsmeans responsive to the opening and subsequent closure of the connectedline circuit for connecting the'finder switch with the engaged linkcircuit an operating circuit for the signaling device ofthe engaged linkcircuit completed upon connection of the finder switch 'therewi'tl1,'andan operator-controlled key common to the link circuits for stopping theoperation of the signaling device.

28. A telephone exchange system compris ing telephone lines, linkcircuits for interconnecting the lines, a signaling device in dividualto each link circuit, a signal comanon to the link circuits, apparatusfor connecting the signal to one of several engaged link circuits to theexclusion of other engaged link circuits, means responsive to Gopies ofthis patent may be obtained for Y 29. A telephone exchange systemcomprisin'g telephone lines, link circuits for interconnecting thelines, a signaling device common to and connectible to any one ofseveral engaged link circuits to the exclusion of other engaged linkcircuits, means common to the link circuits for connecting the signalingdevice to any one of the engaged link circuits, and means individual toeach link circuit and controlled from the respec tive connectedtelephone lines for determining the engaged link circuit with which thesignaling device is to be connected.

In witness whereof, I hereunto subscribe my name this 20th day of April,A. D. 1917.

HENRY r. CLAUSEN.

Washington, D. G.

